WASP-39b is eight times closer to its parent star, WASP-39, than Mercury is to the Sun and it takes only four days to complete an orbit NASA, ESA, and G. Bacon STScI

Just 700 light years away from Earth lies an exoplanet known as WASP-39b. Scientists at Nasa have just made that surprising discovery that this exoplanet has an immense amount of water. The exoplanet has been classified as a "hot Saturn" because it has a mass equal to that of the gas giant and its proximity to its host star is also similar to that of Saturn's proximity with our sun.

Researchers were surprised to find that the alien world contains a lot of water — almost three times the water found on Saturn. However, unlike the solar system gas giant, WASP-39b does not have a ring system. It also has a "puffy" atmosphere, free of clouds, which allowed the Hubble telescope to peer into its atmosphere.

The immense amount of water found in WASP-39b led scientists to assume that the exoplanet may have formed differently than others. According to Nasa, the large amount of water indicates that the exoplanet likely formed far away from its host star, where it was bombarded with icy material.

Researchers also believe that the exoplanet likely travelled inward across its planetary system, likely knocking off other planetary objects on its way, to reach its current location. Researchers believe that WASP-39b's evolution could help us better understand the history of our own solar system planets.

"We need to look outward so we can understand our own solar system," Hannah Wakeford, lead investigator of the Space Telescope Science Institute and the University of Exeter, said in a statement.

The researchers dissected starlight filtering through the exoplanet's atmosphere into component colours, which in turn allowed them to discover evidence of the presence of water. The water was detected as vapour in the atmosphere. The scientists also made use of the Hubble and Spitzer telescopes to develop a detailed spectrum of the WASP-39b's atmosphere — the most complete spectrum of an exoplanet captured till date.

"This spectrum is thus far the most beautiful example we have of what a clear exoplanet atmosphere looks like," said Wakeford.

Using the Nasa/ESA Hubble Space Telescopes as well as data gathered by other telescopes in space and on the ground astronomers have analysed the atmosphere of the exoplanet WASP-39b NASA, ESA, G. Bacon and A. Feild STScI), and H. Wakeford (STScI/Univ. of Exeter

Scientists also discovered that the exoplanet completes one orbit around its host star in four days. WASP-39b is 20 times closer to its host star than the Earth is to the Sun. In other words, the exoplanet's inward journey has resulted in WASP-39b being eight times closer to its star than the Mercury is to the sun.

The alien world is also tidally locked, which means that it shows only one side to its star. Researchers estimate that the planet's temperature is over a scorching 760C. Even the planet's permanent night-side is incredibly hot, thanks to powerful winds that transfer the heat from the day-side of the exoplanet.

"WASP-39b shows exoplanets can have much different compositions than those of our solar system," David Sing of the University of Exeter, a co-author of the new study, said in a statement. "Hopefully this diversity we see in exoplanets will give us clues in figuring out all the different ways a planet can form and evolve."

Once the James Webb Telescope, which is scheduled to launch in 2019, is up and running, Wakeford hopes to use the massive telescope to capture an even more detailed spectrum of WASP-39b. This will likely help researchers gain an even better understanding of how and where this planet was formed.

"Exoplanets are showing us that planet formation is more complicated and more confusing than we thought it was," Wakeford added. And that's fantastic!"